'''
题目：求1!+2!+3!+...+20!的和。

程序分析：此程序只是把累加变成了累乘。


'''

# !/usr/bin/python
# -*- coding: UTF-8 -*-

n = 0
s = 0
t = 1
for n in range(1, 5):
    t *= n
    s += t
    print(n)
print('1! + 2! + 3! + ... + 20! = %d' % s)

# !/usr/bin/python
# -*- coding: UTF-8 -*-

s = 0
l = range(1, 21)


def op(x):
    r = 1
    for i in range(1, x + 1):
        r *= i
    return r


s = sum(map(op, l))
print('1! + 2! + 3! + ... + 20! = %d' % s)


'''



'''









